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ANATOMICAL BASIS OF PERIPHERAL NERVE COMPRESSION

D Athavia*, A P Chaphekar**
*Associate Professor in Anatomy, TNMC Mumbai 400 008. **Lecturer in Surgery, LTMC Sion Mumbai 400 022.

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Contrasting diagnoses from root compression to neuritis were made. EMG suggested C5 involvement and MRI showed C5-C6 space compression, so the paralysis of left deltoid was not matching with MRI findings of compression of the C6 nerve. Following complication of unnecessary surgery, the opposite normal C5 was also affected.

The neuritis of the left C5 has now recovered, but the operative complication still remains.

INTRODUCTION

This is a case history of one of my relatives, which brings into focus, once again the importance of careful history taking and a sound basis of anatomical knowledge in clinical diagnosis and treatment. With the increasing sophistication of imaging techniques, the anatomical knowledge required for their interpretation must also keep pace.

CASE HISTORY WITH DISCUSSION

In October 1994, this relative, a thirty-eight year old male patient working as a purser in the airlines complained of pain in the back of the neck radiating to the left shoulder. A diagnosis of cervical spondylosis was made and mechanical traction was advised. One month later, the shoulder pain worsened and in Italy, he was advised and given an intra-muscular injection of nonsteroidal anti-inflammatory drug in alcohol into the left shoulder. There was dramatic relief of pain but two days later, there was severe pain and inability to abduct the left shoulder and a diagnosis of viral mononeuritis was made.

Since the pain remained intermittent and there was also restriction to abduction at the left shoulder joint, the patient consulted orthopaedic surgeons, neurologists and neurosurgeons and was advised to take plain X-rays of Neck and Left Shoulder - AP and Lateral views (Figs. 1 and 2). He was also advised an EMG and MRI.

The EMG showed C5 involvement and MRI sagittal plane scan showed compression of the nerve root emerging between C5 and C6 vertebrae. This implied that there was a discrepancy between the findings of EMG and MRI, since, EMG showed C5 involvement, while MRI showed C6 involvement, since C6 nerve emerges between C5 and C6 vertebrae. This fact was missed in the interpretation of MRI and loss of abduction at shoulder (C5 myotome) was also missed.

Fig 1 : X-ray neck AP view

Fig 2 : X-ray neck lateral view

Fig 3 : MRI cervical spine

Fig 4 : MRI cervical spine

The compression of C6 nerve on MRI was sub-clinical since it could not possibly cause the symptoms he was having and yet, the patient was operated upon in the following February and two intervertebral discs between C4-C5 and C5-C6 were removed.

Operative findings showed that the compression of C6 nerve was greater than the C5 nerve.

Within one week of surgery, there was root pain in the opposite shoulder with wasting of the right deltoid with brisk triceps jerk. At the end of two weeks, the right deltoid was paralyzed.

Department of Neurophysiology
MR.		38 yrs/M	24.11.94
REF. BY :		EMG : B-1930/94
MEDIAN NERVE		RIGHT	LEFT
Latency at wrist			3.4 ms
Peak to peak amplitude			3.0 ms
Latency at elbow			7.7 ms
Peak to peak amplitude			1.7 mv
Conduction distance			24 cms
Conduction velocity			56 m/sec
F waves			25.1 ms
ULNAR NERVE
Latency at wrist			2.5 ms
Peak to peak amplitude			4.7 mv
Latency at elbow			7.6 ms
Peak to peak amplitude			3.7 mv
Conduction distance			26 cms
Conduction velocity			51 m/sec
F waves			24.0 ms
MEDIAN SENSORY NERVE
Onset latency			2.8 ms
Peak latency			3.5 ms
Amplitude			25.6 uv
ULNAR SENSORY NERVE
Onset latency			2.3 ms
Peak latency			3.0 ms
Amplitude			14.3 uv
NERVE TO DELTOID
Latency		3.5 ms	4.6 ms
Amplitude		2.8 mv	1.1 mv
MUSCLES EXAMINED	AT REST	ON MIN VOLITION	RECRUITMENT
(L) Deltoid	Silent	Very few motor units on maximal volition	Markedly reduced
(L) Triceps	...do...	Normal MUPs	Full
(L) Biceps	...do...	...do...	...do...

 

CONCLUSION

What started off as a simple pain in the left shoulder, took a convoluted course from clinical examination to radiography, from EMG to MRI, from physiotherapy to surgery, from simplicity to complications - all owing to an inadequate focus on history taking and inattention to anatomical details.

Rightly it is said:
For want of a nail
A horse - shoe was lost,
For want of a horse-shoe
A King was lost,
For want of a King
A battle was lost,
For want of a nail
A kingdom was lost.

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REFERENCES

1. Muscle testing and functions - Florence Kendamn and Elizabeth Mcreary. 99-101.
2. Clinical orthopedic rehabilitation - S Brant Brotzman. 384-85.
3. Grants Atlas - (deltoid M). 6-16 and 30-39. (Supraspinatus) 6, 35-36 and 64-93. (Axillary nerve) 6,22,23,24,39,40 and 48. (Infra spinatus) 6,36,39,40 and 48.
4. Text book of Regional Anatomy. RJ Last. (deltoid) 74. (Axillary nerve) 69,125 and 126. (supra/infra spinatus) 72.
5. Adam's Fracture (Disorders of shoulder joint) 124-27.
6. Surgical anatomy - Mcgregor. 435.
7. Grants Method of Anatomy.

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